WO2014031372A1

WO2014031372A1 - Processing flexible glass substrates

Info

Publication number: WO2014031372A1
Application number: PCT/US2013/054473
Authority: WO
Inventors: Sean Matthew Garner; Robert George MANLEY
Original assignee: Corning Incorporated
Priority date: 2012-08-22
Filing date: 2013-08-12
Publication date: 2014-02-27
Also published as: TW201410474A; JP2015532004A; CN104685627B; KR20150046218A; CN104685627A; TWI589443B

Abstract

A method of processing a flexible glass substrate is provided. The method includes providing a substrate stack comprising the flexible glass substrate bonded to a carrier substrate using an inorganic bonding layer that undergoes a structural change upon receiving an energy input. The energy input is provided to the inorganic bonding layer for initiating the structural change. The structural change decreases a bond strength of the inorganic bonding layer for separating the flexible glass substrate from the carrier substrate.

Description

PROCESSING FLEXIBLE GLASS SUBSTRATES

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 61/691904 filed on August 22, 2012 the content of which is relied upon and incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present invention relates to apparatuses and methods for processing thin substrates on carrier substrates, and more specifically, to thin substrates of flexible glass on carrier substrates.

BACKGROUND

[0003] Today, flexible plastic films are commonly used in flexible electronic devices associated with PV, OLED, LCDs, touch sensors, flexible electronics and patterned Thin Film Transistor (TFT) applications.

[0004] Flexible glass substrates offer several technical advantages over flexible plastic technology. One technical advantage is the ability of the glass to serve as a moisture or gas barrier, a primary degradation mechanism in OLED displays, OLED lighting and organic photovoltaic devices. A second advantage is in its potential to reduce overall package size (thickness) and weight through the reduction or elimination of one or more package substrate layers. Other advantages of flexible glass substrates include benefits in optical transmission, dimensional stability, thermal capability and surface quality.

[0005] As the demand for thinner/flexible glass substrates (less than 0.3 mm thick) is driven into the electronic display industry, panel manufacturers faced a number of challenges to handling and adapting to the thinner/flexible glass substrates. One option is to process thicker sheets of glass then etch or polish the panel to thinner overall net thickness. This enables the use of existing panel fabrication infrastructure based on substrates 0.3 mm thick or thicker, but adds finishing costs to the end of the process along with a potential reduction in yield. A second approach is to re-engineer the existing panel process for thinner substrates. Glass loss in the process is a major interruption, and significant capital would be required for minimizing handling loss in either a sheet-to-sheet process based on nonsupported flexible glass substrates. A third approach is to utilize Roll-to-Roll processing technologies or technologies based on roller handling for the thin flexible glass substrates.

[0006] What is desired is a carrier approach that utilizes the existing capital infrastructure of the manufacturers based on rigid substrates 0.3 mm or thicker and enables processing of thin, flexible glass substrates, i.e., glass having a thickness no greater than about 0.3 mm thick.

SUMMARY

[0007] The present concept involves bonding a thin sheet, for example, a flexible glass substrate, to a carrier substrate using an inorganic bonding layer that changes structure upon its receiving an energy input, such as thermal energy. The structural change decreases a bond strength of the inorganic bonding layer for separating the flexible glass substrate from the carrier substrate.

[0008] One commercial advantage to the present approach is that manufacturers will be able to utilize their existing capital investment in processing equipment while gaining the advantages of the thin glass sheets for PV, OLED, LCDs, touch sensors, flexible electronics and patterned Thin Film Transistor (TFT) electronics, for example.

[0009] According to a first aspect, a method of processing a flexible glass substrate comprises:

providing a substrate stack comprising the flexible glass substrate bonded to a carrier substrate using an inorganic bonding layer that undergoes a structural change upon receiving an energy input; and

providing the energy input to the inorganic bonding layer for initiating the structural change, the structural change decreasing a bond strength of the inorganic bonding layer for separating the flexible glass substrate from the carrier substrate.

[0010] According to a second aspect, there is provided the method of aspect 1 , wherein the energy input is thermal energy, the method comprising heating the inorganic bonding layer to a temperature of at least about 250 °C.

[0011] According to a third aspect, there is provided the method of any one of aspect 1 or

2, wherein the energy input is optical energy that results in heating the inorganic bonding layer to a temperature of at least about 250 °C.

[0012] According to a fourth aspect, there is provided the method of any one of aspects 1 -

3, wherein the inorganic bonding layer comprises an inorganic bonding material located along a perimeter of the flexible glass substrate.

[0013] According to a fifth aspect, there is provided the method of any one of aspects 1-4, wherein the inorganic bonding layer is heated locally using a laser.

[0014] According to a sixth aspect, there is provided the method of any one of aspects 1-5, wherein the structural change includes crystallization.

[0015] According to a seventh aspect, there is provided the method of any one of aspects 1- 6, wherein the structural change includes increasing a porosity of the inorganic bonding layer.

[0016] According to an eighth aspect, there is provided the method of any one of aspects 1-

7, wherein the structural change includes increasing a microfracture of the inorganic bonding layer.

[0017] According to a ninth aspect, there is provided the method of any one of aspects 1-8 further comprising removing the flexible glass substrate from the carrier substrate after providing the energy input to the inorganic bonding layer.

[0018] According to a tenth aspect, there is provided the method of any one of aspects 1-9 further comprising applying an electrical component to the flexible glass substrate.

[0019] According to an eleventh aspect, there is provided the method of any one of aspects 1-10, wherein the flexible glass substrate has a thickness that is no greater than about 0.3 mm.

[0020] According to a twelfth aspect, there is provided the method of any one of aspects 1 - 1 1, wherein the carrier substrate comprises glass.

[0021] According to a thirteenth aspect, there is provided the method of any one of aspects 1-12, wherein the bonding material comprises one or more of a glass, a glass ceramic and a ceramic.

[0022] According to a fourteenth aspect, there is provided the method of any one of aspects 1-13, wherein the bonding material comprises carbon.

[0023] According to a fifteenth aspect, there is provided the method of any one of aspects 1-14, wherein the bonding material comprises silicon.

[0024] According to a sixteenth aspect, there is provided the method of any one of the aspects 1-15 comprising at least partially de-bonding the flexible glass substrate and the carrier substrate when changing the structure of the bonding material.

[0025] According to a seventeenth aspect, there is provided the method of any one of the aspects 1-16, wherein the input energy is thermal energy and the method comprising heating the bonding material up to a temperature of at least about 250 °C without a reduction of the bond strength.

[0026] According to an eighteenth aspect, there is provided the method of any one of the aspects 1-17, wherein the input energy is optical energy and the method comprising heating the bonding material up to a temperature of at least about 250 °C without a reduction of the bond strength.

[0027] According to a nineteenth aspect, a method of processing a flexible glass substrate comprises:

providing a carrier substrate having a glass support surface; providing a flexible glass substrate having first and second broad surfaces;

bonding the first broad surface of the flexible glass substrate to the glass support surface of the carrier substrate using an inorganic bonding layer; and

changing a structure of the inorganic bonding layer and reducing a bond strength between the flexible glass substrate and the carrier substrate for removing the flexible glass substrate from the carrier substrate.

[0028] According to a twentieth aspect, there is provided the method of aspect 19 comprising providing an energy input to the inorganic bonding layer for changing the structure of the inorganic bonding layer and reducing the bond strength between the flexible glass substrate and the carrier substrate.

[0029] According to a twenty- first aspect, there is provided the method of aspect 20, wherein the energy input is thermal energy, the method comprising heating the inorganic bonding layer to a temperature of at least about 250 °C.

[0030] According to a twenty-second aspect, there is provided the method of any one of aspect 20 or 21 , wherein the energy input is optical energy, the method comprising heating the inorganic bonding layer to a temperature of at least about 250 °C.

[0031] According to a twenty-third aspect, there is provided the method of any one of aspects 19-22, wherein the inorganic bonding layer is heated locally using a laser.

[0032] According to a twenty- fourth aspect, there is provided the method of any one of aspects 19-23, wherein the inorganic bonding layer is heated using a flashlamp.

[0033] According to a twenty- fifth aspect, there is provided the method of any one of aspects 19-24, wherein the flexible glass substrate has a thickness that is no greater than about 0.3 mm.

[0034] According to a twenty-sixth aspect, a substrate stack comprises:

a carrier substrate having a glass support surface;

a flexible glass substrate supported by the glass support surface of the carrier substrate; and

an inorganic bonding layer that bonds the flexible glass substrate to the carrier substrate, the inorganic bonding layer comprising a bond material that changes structure and reduces a bond strength between the flexible glass substrate and the carrier substrate for removing the flexible glass substrate from the carrier substrate

[0035] According to a twenty- seventh aspect, there is provided the substrate stack of aspect 26, wherein the bond material comprises carbon.

[0036] According to a twenty-eighth aspect, there is provided the substrate stack of any one of aspect 26 or 27, wherein the bonding material comprises silicon.

[0037] According to a twenty-ninth aspect, there is provided the substrate stack of aspect

26, wherein the bond material comprises at least one of a glass, a glass ceramic and a ceramic.

[0038] According to a thirtieth aspect, there is provided the substrate stack of aspect 26, wherein the bond material comprises amorphous silicon.

[0039] According to a thirty- first aspect, there is provided the substrate stack of any one of aspects 26-30, wherein the structural change includes crystallization.

[0040] According to a thirty-second aspect, there is provided the substrate stack of any one of aspects 26-31, wherein the flexible glass substrate has a thickness that is no greater than about 0.3 mm.

[0041] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the invention as exemplified in the written description and the appended drawings and as defined in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework to understanding the nature and character of the invention as it is claimed.

[0042] The accompanying drawings are included to provide a further understanding of principles of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain, by way of example, principles and operation of the invention. It is to be understood that various features of the invention disclosed in this specification and in the drawings can be used in any and all combinations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 is a side view of an embodiment of a substrate stack including a flexible glass substrate that is carried by a carrier substrate;

[0044] FIG. 2 is an exploded, perspective view of the substrate stack of FIG. 1 ;

[0045] FIG. 3 illustrates an embodiment of a method of processing the flexible glass substrate and substrate stack of FIG. 1 ;

[0046] FIG. 4 is a top view of an embodiment of a substrate stack with a flexible glass substrate and carrier substrate having different sizes;

[0047] FIG. 5 is a top view of another embodiment of a substrate stack with a flexible glass substrate and carrier substrate having different shapes; [0048] FIG. 6 is a top view of an embodiment of a substrate stack having a bonding layer applied over a glass support surface of the carrier substrate;

[0049] FIG. 7 is a top view of another embodiment of a substrate stack having a bonding layer applied over a glass support surface of the carrier substrate;

[0050] FIG. 8 is a top view of another embodiment of a substrate stack having a bonding layer applied over a glass support surface of the carrier substrate;

[0051] FIG. 9 illustrates x-ray diffraction data for a bonding layer at room temperature;

[0052] FIG. 10 illustrates x-ray diffraction data for the bonding layer of FIG. 9 at 180 °C;

[0053] FIG. 11 illustrates x-ray diffraction data for the bonding layer of FIG. 9 at 250 °C illustrating increased crystallization of the bonding layer;

[0054] FIG. 12 illustrates absorbance of a carbon-based bonding layer;

[0055] FIG. 13 illustrates an embodiment of a method of processing the substrate stack with an amorphous silicon bonding layer;

[0056] FIG. 14A illustrates a process of applying thermal energy to the bonding layer through the flexible glass substrate;

[0057] FIG. 14B illustrates a process of applying thermal energy to the bonding layer through the carrier substrate;

[0058] FIG. 15 illustrates another embodiment of a method of processing the substrate stack with an amorphous silicon bonding layer;

[0059] FIG. 16 illustrates another embodiment of a method of processing the substrate stack with an amorphous silicon bonding layer;

[0060] FIG. 17 is a top view of an embodiment of a substrate stack having a bonding layer applied over a glass support surface of the carrier substrate;

[0061] FIG. 18 is a top view of an embodiment of a substrate stack for forming a plurality of desired parts; and

[0062] FIG. 19 illustrates an embodiment of a method of releasing a flexible glass substrate from a carrier substrate.

DETAILED DESCRIPTION

[0063] Embodiments described herein generally relate to processing of flexible glass substrates, sometimes referred to herein as device substrates. The flexible glass substrates may be part of a substrate stack that generally includes a carrier substrate and the flexible glass substrate bonded thereto by an inorganic bonding layer. As used herein, the term "inorganic materials" refers to compounds that are not hydrocarbons or their derivatives. As will be described in greater detail below, the bonding layer undergoes a structural change upon receipt of an energy input. Upon receipt of the energy input by the bonding layer, the structural change decreases or otherwise changes a bond strength of the bonding layer for more readily separating the flexible glass substrate from the carrier substrate as compared to before the energy input.

[0064] Referring to FIGS. 1 and 2, a substrate stack 10 includes a carrier substrate 12 and a flexible glass substrate 20. The carrier substrate 12 has a glass support surface 14, an opposite support surface 16 and a periphery 18. The flexible glass substrate 20 has a first broad surface 22, an opposite, second broad surface 24 and a periphery 26. The flexible glass substrate 20 may be "ultra-thin" having a thickness 28 of about 0.3 mm or less including but not limited to thicknesses of, for example, about 0.01-0.05 mm, about 0.05-0.1 mm, about 0.1-0.15 mm and about 0.15-0.3 mm.

[0065] The flexible glass substrate 20 is bonded at its first broad surface 22 to the glass support surface 14 of the carrier substrate 12 using a bonding layer 30. The bonding layer may be an inorganic bonding layer comprising an inorganic bonding material. When the carrier substrate 12 and the flexible glass substrate 20 are bonded to one another by the bonding layer 30, the combined thickness 25 of the substrate stack 10 may be the same as single glass substrate having increased thickness as compared to the thickness of the flexible glass substrate 20 alone, which may be suitable for use with existing device processing infrastructure. For example, if the processing equipment of a device processing infrastructure is designed for a 0.7 mm sheet, and the flexible glass substrate 20 has a thickness 28 of 0.3 mm, then thickness 32 of the carrier substrate 12 may be selected to be something no greater than 0.4 mm, depending, for example, on thickness of the bonding layer 30.

[0066] The carrier substrate 12 may be of any suitable material including glass, glass- ceramic or ceramic, as examples, and may or may not be transparent. If made of glass, the carrier substrate 12 may be of any suitable composition including alumino-silicate, boro- silicate, alumino-boro-silicate, soda-lime-silicate, and may be either alkali containing or alkali- free depending upon its ultimate application. The thickness 32 of the carrier substrate 12 may be from about 0.2 to 3 mm, for example 0.2, 0.3, 0.4, 0.5, 0.6, 0.65, 0.7, 1.0, 2.0, or 3 mm, and may depend upon the thickness 28 of the flexible glass substrate 20, as noted above. Additionally, the carrier substrate 12 may be made of one layer, as shown, or multiple layers (including multiple thin sheets) that are bonded together to form a part of the substrate stack 10.

[0067] The flexible glass substrate 20 may be formed of any suitable material including glass, glass-ceramic or ceramic, as examples, and may or may not be transparent. When made of glass, the flexible glass substrate 20 may be of any suitable composition, including alumino-silicate, boro-silicate, alumino-boro-silicate, soda- lime-silicate, and may be either alkali containing or alkali free depending upon its ultimate application. The thickness 28 of the flexible glass substrate 20 may be about 0.3 mm or less, such as about 0.2 mm or less, such as about 0.1 mm, as noted above. As noted herein, the flexible glass substrate 20 may be the same size and/or shape or of a different size and/or shape as the carrier substrate 12.

[0068] Referring to FIG. 3, a releasable bonding method 40 is illustrated as part of the processing of the flexible glass substrate 20. At step 42, the carrier substrate 12 and the flexible glass substrate 20 are selected based on, for example, their sizes, thicknesses, materials and/or end uses. Once the carrier substrate 12 and the flexible glass substrate 20 are selected, the bonding layer 30 may be applied to one or both of the glass support surface 14 and the first broad surface 22 of the flexible glass substrate 20 at step 44. Any suitable methods may be used for applying the bonding layer 30, such as one or more of a pressurized application, such as through a nozzle, spreading, melting, spin casting, spraying, dipping, vacuum or atmospheric deposition, etc.

[0069] At step 46, the flexible glass substrate 20 is adhered or otherwise bonded to the carrier substrate 12 using the bonding layer 30. To achieve a desired bond strength between the flexible glass substrate 20 and the carrier substrate 12, bonding material forming the bonding layer 30 may be heated, cooled, dried, mixed with other materials, reaction induced, pressure may be applied, etc. As used herein, "bond strength" refers to any one or more of dynamic shear strength, dynamic peel strength, static shear strength, static peel strength and combinations thereof. Peel strength, for example, is the force per unit width necessary to initiate failure (static) and/or maintain a specified rate of failure (dynamic) by means of a stress applied to one or both of the flexible glass substrate and carrier substrate in a peeling mode. Shear strength is the force per unit width necessary to initiate failure (static) and/or maintain a specified rate of failure (dynamic) by means of a stress applied to one or both of the flexible glass substrate and carrier substrate in a shear mode. Any suitable methods can be used to determine bond strength including any suitable peel and/or shear strength test as a change in the bond strength is a comparison of the bond strength measured before and after the desired energy input to the bonding layer 30.

[0070] Steps 48 and 50 relate to releasing or de-bonding the flexible glass substrate 20 from the carrier substrate 12 so that the flexible glass substrate 20 can be removed from the carrier substrate 12. Before and/or after releasing the flexible glass substrate 20 from the carrier substrate 12, the flexible glass substrate 20 may be processed, for example, in the formation of a display device, such as an LCD, OLED or TFT electronics or other electronic devices such as a touch sensor or photovoltaic. For example, electrical components or color filters may be applied to the second broad surface 24 of the flexible glass substrate 20 (FIGS. 1 and 2). Additionally, final electronic components can be assembled or combined with the flexible glass substrate 20 before its release from the carrier substrate 12. For example, additional films or glass substrates can be laminated to the surface of the flexible glass substrate 20 or electrical components such as flex circuits or ICs can be bonded. Once the flexible glass substrate is processed, an energy input 47 may be applied to the bonding layer 30 that changes a structure of the bonding layer 30 at step 48. As will be described below, the structure change decreases the bond strength of the bonding layer 30 to facilitate separation of the flexible glass substrate 20 from the carrier substrate 12 as compared to before the energy input at step 48. At step 50, the flexible glass substrate 20 is removed from the carrier substrate 12. The extraction may be accomplished, for example, by peeling the flexible glass substrate 20 or a portion thereof from the carrier substrate 20. A peel force is generated by applying a force F to one or both of the substrates at an angle to a plane P extending through the bonding layer 30.

Carrier Substrate and Flexible Glass Sheet Selection

[0071] The carrier substrate 12 and the flexible glass substrate 20 may be formed of the same, similar or of different materials. In some embodiments, the carrier substrate 12 and the flexible glass substrate 20 are formed of glass, a glass ceramic or a ceramic material. The carrier substrate 12 and the flexible glass substrate 20 may be formed using the same, similar or different forming processes. For example, a fusion process (e.g., downdraw process) forms high quality thin glass sheets that can be used in a variety of devices such as flat panel displays. Where different materials are used, it may be desirable to match coefficient of thermal expansion values. Glass sheets produced in a fusion process have surfaces with superior flatness and smoothness when compared to glass sheets produced by other methods. The fusion process is described in U.S. Patent Serial Nos. 3,338,696 and 3,682,609. Other suitable glass sheet forming methods include a float process, a re-draw process and slot draw method. The flexible glass substrate 20 (and/or the carrier substrate 12) may also include temporary or permanent protective or other type of coating layers on one or both of its first and second broad surfaces 22 and 24.

[0072] One or more of the dimensions and/or shapes of the carrier substrate 12 and flexible glass substrate 20 may be about the same and/or different. For example, referring briefly to FIG. 4, a carrier substrate 12 is illustrated having substantially the same shape as the flexible glass substrate 20, but having one or more dimensions that are greater than the flexible glass substrate 20. Such an arrangement allows a peripheral area 52 of the carrier substrate 12 to extend outwardly beyond the flexible glass substrate 20 about an entire or at least a portion of a periphery 26 of the flexible glass substrate 20. As another example, FIG. 5 illustrates an embodiment where the flexible glass substrate 20 is a different shape, having different dimensions than the carrier substrate 12. Such an arrangement can allow for only portions 54 of the periphery 18 of the carrier substrate 12 to extend outwardly beyond the periphery 26 of the flexible glass substrate 20. While rectangles and circular shapes are illustrated, any suitable shapes including irregular shapes maybe used depending on the desired stack configuration. Further, the carrier substrate 12 may have its edges rounded, finished and/or ground to tolerate impacts and to facilitate handling. Surface features such as grooves and/or pores may also be provided on the carrier substrate 12. The grooves, pores and/or other surface features may facilitate and/or inhibit bonding material location and/or adhesion. Selection and Application of the Bonding Layer

[0073] The bonding layer 30 may include one or more bonding materials that undergo a structural change upon receipt of an energy input. For example, the bonding layer 30 may include inorganic materials, and may include materials such as glass, glass ceramics, ceramics and carbon containing materials. In some embodiments, the bonding layer 30 may consist of carbon forming a carbon bonding layer. In some embodiments, the bonding layer 30 may consist of silicon forming a silicon bonding layer. Various exemplary bonding materials are described below. Any suitable methods may be used for applying the bonding layer 30, such as one or more of a pressurized application, such as through a nozzle, spreading, melting, spin casting, spraying, dipping, vacuum or atmospheric deposition, etc.

[0074] The bonding layer 30 may be applied in any suitable pattern and/or shape.

Referring to FIG. 6, the bonding layer 30 is applied over an area Ai of the glass support surface 14 that is at least about 50 percent of an area A2 covered by the flexible glass substrate 20, such as substantially all of the area A₂. In some embodiments, Ai may be less than about 50 percent of A₂, such as no more than about 25 percent of A₂. The bonding layer 30 may extend beyond the perimeter of the flexible glass substrate 20 or the bonding layer 30 may be contained within the perimeter of the flexible glass substrate 20. Referring to FIG. 7, the bonding layer 30 may be applied continuously along a predetermined path, such as area A3 that extends about a periphery of A2 (i.e., a continuous perimeter bond), leaving an unbonded region R that is bounded by the bonding layer 30. Referring to FIG. 8, the bonding layer 30 may be formed of discrete bonding segments 60 that are spaced from each other. In the embodiment of FIG. 8, the discrete bonding segments are in the form of individual lines. Any other suitable shapes may be used, such as circles, dots, random shapes and

combinations of the various shapes.

Changing the Structure of the Bonding Layer

[0075] An energy input is provided to the bonding layer 30 that changes or is used to change a structure of the bonding layer 30. The structure change decreases the bond strength of the bonding layer 30 as compared to before the energy input to facilitate separation of the flexible glass substrate 20 from the carrier substrate 12. The bond strength can be reduced by reducing the cohesive strength of the bonding layer 30, itself, and/or the adhesive strength between the bonding layer 30 and/or the flexible glass substrate 20 and carrier substrate 12. The type of the energy input depends, at least in part, on the bonding material used in the bonding layer 30. The following provides non- limiting examples of bonding materials used for providing the bonding layer 30 and input energies and are not meant to be limiting. These initial examples illustrate crystallization of the bonding layer 30 with the input of energy, which decrease the bond strength of the bonding layer 30. Such a decrease in the bond strength facilitates separation of the flexible glass substrate 20 from the carrier substrate 12 without damage to the flexible glass substrate 20.

Example 1

[0076] A bismuth zinc borate (BZB) glass was formed and ground to a less than 20 μιη average particle size. The BZB glass particles were passed through a 350 mesh screen and mixed 75 wt% with a binder in a helicone mixer at 100 °C. The thermally heated paste was dispensed with a pipette onto a carrier substrate, and a bonding layer was formed on the carrier substrate using a doctor blade. Bonding layers were formed of approximate thicknesses of 25 μιη, 75 μιη and 125 μιη for evaluation purposes. Smaller thicknesses are possible by use of smaller glass particle sizes or through deposition methods of forming the bonding layer. After the bonding layer was formed, it underwent the following thermal profile:

a. Room temperature to 200 °C @ 5 °C/min.

b. 200 °C hold for 1 hour to burn off binder.

c. 200 °C to 400 °C at 5 °C/min.

d. 400 °C hold for one hour.

e. Cool.

X-ray diffraction showed bonding layer crystallization of bismuth oxide, bismuth borate, zinc oxide and boron oxide due, at least in part, to the thermal ramp and particle size of the BZB glass particles. This crystallization reduces the bond strength provided by the bonding layer. Example 2

[0077] A phosphate glass powder was prepared by grinding and passing through a 325 mesh screen. The phosphate glass powder was then mixed 83 wt% with a CI 8 binder. The heated paste was applied to a substrate using a doctor blade to produce approximate evaluation thicknesses of 25 μιη and 75 μιη. Smaller thicknesses are possible by use of smaller glass particle sizes or through deposition methods of forming the bonding layer. After the bonding layer was formed, it underwent the following thermal profile:

a. Room temperature to 200 °C at 1 °C/min.

b. 200 °C hold for 1 hour.

c. 200-400 °C at 1 °C/min.

d. 400 °C hold for 1 hour.

e. Cool.

X-ray diffraction showed bonding layer crystallization of barium oxide, zinc phosphate, zinc phosphide, zinc oxide and barium zinc phosphide due to, at least in part, the thermal profile and particle size of the phosphate glass particles. This crystallization reduces the bond strength provided by the bonding layer.

Example 3

[0078] A small bulk piece of tin fluorophosphate glass was placed between two

EAGLE2000® brand (an alkali- free alumino-boro-silicate glass) substrates 0.7 mm in thickness, commercially available from Corning Incorporated, Corning NY. This stack was placed in an oven with a weight on top to provide a bonding force. Six different thermal profiles were used to determine the temporary bonding and de-bonding of the substrates. All thermal ramps to higher temperatures were performed at 5 °C/min.

1. The stack was heated to a maximum temperature of 150 °C. No visible sign of phosphate glass melting or bonding was observed.

2. The stack was heated to a maximum temperature of 160 °C. No visible sign of phosphate glass melting or bonding was observed.

3. The stack was heated to a maximum temperature of 170 °C. Bonding was observed between the EAGLE2000® - phosphate glass - EAGLE2000® substrates with no obvious signs of crystallization in the bonding layer.

4. The stack was heated to a maximum temperature of 200 °C. Possible signs of crystallization were observed in the bonding layer.

5. The stack was heated to a maximum temperature of 180 °C and bonding between the EAGLE2000® - phosphate glass - EAGLE2000® substrates was observed with no visible signs of crystallization of the bonding layer. The stack was then heated to a maximum temperature of 400 °C and signs of crystallization were observed throughout the bonding layer along with a change in the mechanical properties and density of the bonding layer.

6. The stack was heated to a maximum temperature of 180 °C and bonding between the EAGLE2000® - phosphate glass - EAGLE2000® substrates was observed with no visible signs of crystallization of the bonding layer. The stack was then heated to a maximum temperature of 250 °C and signs of crystallization were observed, but less crystallization than was observed at 400 °C. The EAGLE2000® substrates were then separated.

[0079] The examples above illustrate that glass substrates can be bonded together using a bonding layer of an inorganic material. After a possible fabrication step, the bonding layer can be heated to an even higher temperature to induce crystallization and/or other structural changes in the bonding layer. Due to this structural change, the glass substrates can be separated with less force than before the structural change in the bonding layer.

[0080] FIGS. 9, 10 and 1 1 illustrate crystallization of the bonding layer 30 of Example 3 at higher temperature exposures. FIG. 9 illustrates the phosphate glass bonding layer as formed, FIG. 10 illustrates the phosphate glass bonding layer at 180 °C and FIG. 1 1 illustrates the phosphate glass bonding layer at 250 °C. Comparing FIGS. 9 and 10, it can be seen that slight crystallization was present in the phosphate glass at as formed and at 180 °C. FIG. 11 illustrates much higher levels of crystallization present in the phosphate glass at 250 °C, which lowers the bond strength and improves de-lamination of the flexible glass substrate upon application of a separation force. This shows that the two substrates can be bonded together and survive a thermal process. The flexible glass substrate 30 can then be de-bonded from the carrier substrate 12 upon crystallization of the bonding layer 30.

[0081] It should be noted that optimization of the bonding material should occur for the specific device fabrication process used. For example, for an a-Si or p-Si TFT process with a fabrication temperature of about 250 °C or more, such as about 350 °C or more, such as between about 250 °C and about 600 °C, a bonding material may be selected having a de- bond thermal exposure of greater than 250 °C or more, such as 350 °C or more, such as 600 °C or more to reduce any likelihood of unintended de-bonding. However, the thermal exposure to the fabricated device or other components should be selected to be below that which may damage any device electronics or other components. In some embodiments, there may be substantially no or little (e.g., less than about 50 percent, such as less than about 25 percent, such as less than about 10 percent, such as less than about 5 percent, such as less than about 1 percent) reduction in the bond strength of the bonding layer 30 up to the target de-bond thermal exposure. Thus, de-bonding materials can be optimized for different device fabrication scenarios. Also, the application of energy 47 to the bonding layer 30 can be localized to the bonding layer 30, itself. For example, the energy source can be optimized so that the bonding layer 30 absorbs most of the energy 47 which results in lower thermal effect on the flexible substrate 20, carrier substrate 12, or any device layers on the flexible substrate 20.

Example 4

[0082] For this example, an 80 molar % SnO and 20 molar % P2O5 glass bonding material composition was used. Pieces of this glass were placed between two samples of EAGLE XG® (an alkali-free alumino-boro-silicate glass, available from Corning Incorporated, Corning, NY)that were 5cm x 5cm. Various samples then underwent thermal cycles to determine at what temperature the glass bonded to EAGLE XG® and at what temperature the ABR glass crystallized.

[0083] As a first trial, the stack of EAGLE XG® and bonding material was placed in a furnace with a 375 g weight on top. The furnace was heated to 320 °C at 5 °C/min, held for one hour, and then cooled. The bonding material was observed to melt and bond to the EAGLE XG® substrate. The bonding material remained optically clear. The bonding material adhered only to one of the two EAGLE XG® substrates, though, possibly due to thermal expansion mismatch. For actual implementation, the bonding material can be adjusted to CTE match the display glass substrate.

[0084] As a second trial, a sample stack similar to the above example was built and then underwent a thermal cycle up to 350 °C. This caused the bonding material to crystallize and become optically scattering. In this case, the bonding material failed cohesively within itself and the EAGLE XG® glass was easily separated.

[0085] These trials with the bonding material demonstrate it is possible to adhere an inorganic adhesive to display glass and then cause crystallization to occur at a higher temperature. One prophetic example scenario could be to:

A. Bond the display glass substrate to the processing carrier at a temperature above which the device will be built. (320 °C for example);

B. Build the display device at a temperature below the bond temperature (<320 °C);

C. Crystallize the bonding material to reduce its adhesion between the substrate glass and carrier. For example, this would occur at a temperature above the bond temperature (350 °C for example.) If the fabricated device cannot survive this temperature, a localized laser exposure or other absorbing energy could be used to differentially heat the bond glass; and

D. Separate the display glass substrate from the processing carrier.

Example 5

[0086] A thin S1O2 bonding layer was formed using a hydrogen silsesquioxane solution, such as Fox-25, available from Dow Corning. To fabricate the stack, the procedure included the following:

a. Using a 5 cm x 5 cm as a glass carrier substrate (EAGLE2000®) 0.7 mm in thickness.

b. Spin casting the hydrogen silsesquioxane solution onto the carrier substrate at 300 rpm for 15 seconds to form the bonding layer. Other liquid dispensing and film forming methods may be possible for larger scale applications.

c. Applying the device substrate to the bonding layer before drying of the bonding layer. The device substrate was the same configuration as the carrier substrate. d. Placing the stack on a hot plate at room temperature with a weight on top to supply a maximum bonding pressure of 100 kPa.

e. Heating the hot plate to 175 °C and holding for 5-15 minutes and then up to 250 °C for 5-15 minutes.

f. Cooling the hot plate to 175 °C and holding for 5 minutes. It was observed that the bond strength was greatly affected by this initial thermal cycle used to drive off solvent.

[0087] The process of Example 5 can create a high shear strength bond between the carrier substrate and the device substrate. It was observed that it was relatively difficult to separate the device substrate from the carrier substrate by applying a shear force using two pieces of tape on each of the carrier substrate and the device substrate. By applying a peeling force, however, separation of the device substrate from the carrier substrate was relatively easy. Further strength reduction was also achieved by heating the bonding layer to over 350 °C.

[0088] The change in the structure of the bonding layer may result in changes other than crystallization, such as inducing a volume change of the bonding material, inducing a density change of the bonding material, inducing microfractures within the bonding layer, inducing a cohesive failure in the bonding material and increasing an etch sensitivity of the bonding material. While one or more of the above bonding materials illustrate crystallization and/or other structural changes of the bonding layer, other materials may be used to form the bonding layer. For example, a bonding layer that includes carbon may be used to releasably bond the flexible glass substrate and the carrier substrate.

Example 6

[0089] A bonding layer including carbon was formed from a phenolic resin solution. This process utilized a phenol-formaldehyde copolymer and created samples with a spin casting and thermal cure process. The process steps included:

a. Spin casting a diluted phenolic resin solution of 70 wt% resin and 30 wt% DI water at 3 krpm for 30 seconds onto the carrier substrate resulting in a bonding layer of no more than 10 μιη thickness.

b. Placing the carrier substrate with the bonding layer and device substrate placed thereon on a hot plate at room temperature. A weight was applied that produced a maximum bonding pressure of greater than 100 kPa.

c. Heating the hot plate to 150 °C and holding for about 10 minutes and then cooling back to room temperature.

d. Cycling the stack in a furnace in air up to 400 °C for one hour and then cooling.

[0090] Using this process, the device substrates were bonded to the carrier substrates that survived shear pull tests and could be separated when a peeling force was applied due, at least in part, to the carbon bonding layer left behind after heating and the increased porosity formed in the bonding layer during the heating. Both the device substrate and the carrier substrate were formed of EAGLE2000® (8 cm x 12 cm) substrates 0.7 mm in thickness.

[0091] Additional screening tests were performed on stacks formed in accordance with Example 6. The stacks were cycled in a 500 °C furnace in air for one hour, which resulted in severe oxidation of the bonding layer. This oxidation of the carbon bonding layer can be used to de-bond the device substrate from the carrier substrate. Because the oxidized carbon vaporizes, the carbon bonding layer can be easily removed to clean the carrier substrate for re-use.

[0092] The bond strength between a flexible glass substrate 20 and a carrier substrate 12 can be reduced by oxidizing the carbon-based bonding layer. Heating of the bonding layer 30, such as in Example 5, in the presence of oxygen to a temperature of about 500 °C can cause the carbon to oxidize. In the presence of ozone, oxidation of the carbon bonding layer can occur at temperatures less than 500 °C. While it may not be acceptable to heat a fully assembled device substrate to up to 500 °C, in some embodiments, the bonding layer may be heated locally with a laser to a temperature that requires oxidation. [0093] Referring to FIG. 12, absorbance of a carbon-based bonding layer 30 is illustrated. A laser may be used to locally heat and oxidize the carbon-based bonding layer 30 (or any one or more of the bonding materials described herein). The carbon-based bonding layer 30 may be applied as a perimeter bond (FIG. 7) to facilitate the localized heating of the carbon- based bonding layer 30 by the laser, providing greater access to the carbon-based bonding layer 30 due to its proximity to the perimeter of the flexible glass substrate 20. FIG. 12 illustrates the absorption spectrum for the carbon-based bonding layer 30 resulting from the phenolic resin described in Example 6 above. As can be seen, absorbance increases in the visible and UV spectrum, enabling heating of the bonding material useful for thermal oxidation. Dopants may be added to the bonding layer to increase the amount of radiation that is absorbed.

[0094] For the laser heating or other heating methods that target energy absorption predominantly in the bonding layer 30, the energy source should be tuned for the absorption spectra of the bonding layer. In this case, the laser or other energy is applied through the flexible glass substrate 20 or the carrier substrate 12. The flexible glass substrate 20 or carrier substrate 12 can be at least partially transparent to this energy. The majority of the energy passes through the flexible glass substrate 20 or carrier substrate 12 and is then absorbed by the bonding layer 30. In the case of the carbon-based film spectrum shown in FIG. 12, this can be accomplished by use of a red, green, blue, or UV optical source. Laser, LED, and flashlamp are examples of optical sources. The spectrum in FIG. 12 shows strong absorption at wavelengths less than 700 nm. Comparing the absorption of typical glass carriers and the carbon-based film, an exposure wavelength in the range of 400 nm to 550 nm may be most efficient.

[0095] As indicated above, bonding materials used to form the bonding layers 30 can be selected based on a particular device fabrication scenario. To demonstrate compatibility of the bonding layer 30 with Si TFT fabrication processes, the following steps were performed on 8 cm x 12 cm carrier substrates and device substrates formed of EAGLE2000® substrates bonded as described in Example 4. After each step, the shear strength was tested by attempting to pull the device substrate from the carrier substrate in the plane of the bonding layer. All stack samples survived the shear stress test and could more easily be peeled apart after a final 400 °C furnace cycle. To perform this evaluation, substrates were bonded together in an offset configuration to allow portions of the substrates that were non-bonded facilitate shear and peel testing. The screening process included:

1. Room temperature DI water soak, 2 gun blow dry, complete dry with 100 °C hot plate for 5 minutes.

2. Concentrated photoresist developer soak for 5 minutes, DI water rinse, 2 gun blow dry and 100 °C hot plate dry for 5 minutes.

3. Chrome etchant soak for 5 minutes, DI water rinse, 2 gun blow dry and 100 °C hot plate dry for 5 minutes.

4. Gold etchant soak 5 minutes, DI water rinse, 2 gun blow dry and 100 °C hot plate dry for 5 minutes.

5. DI water soak at 95-100 °C for 15 minutes, N₂ gun blow dry and 100 °C hot plate dry for 5 minutes.

6. Furnace cycle at 400 °C in air with 1 hour hold.

[0096] In yet other embodiments, the bonding layer 30 may be formed of amorphous silicon and anodic bonding may be utilized to bond the flexible glass substrate 12 to the carrier substrate 20. The amorphous silicon may be deposited on either or both of the flexible glass substrate 12 and the carrier substrate 20. An electrical bias may be applied across the substrate stack (FIG. 1), resulting in enriched oxygen layers at the interfaces between the bonding layer 30, the flexible glass substrate 12 and the carrier substrate 20 which react with the silica and form an amorphous silica bonding layer that bonds the flexible glass substrate 12 and the carrier substrate 20. Heat and/or pressure may or may not be used for bonding. For example, in the absence of any applied pressure, the flexible glass substrate 12 may be bonded to the carrier substrate 12 using amorphous silicon at lower temperatures (e.g., less than 500 °C) than if a pressure is applied (e.g., greater than 700 °C). It may be desirable, in some embodiments, to utilize a relatively lower temperature to inhibit any warping or other potential defects in the flexible glass substrate 20 that may result from higher temperatures.

[0097] As above, the bonding strength of the bonding layer 30 formed of amorphous silicon may be reduced by an energy input. The energy provided to the bonding layer 30 may result in a transformation of the amorphous silicon to either polycrystalline silicon or to a melted structure, utilizing the material characteristics of the transformation to debond the flexible glass substrate 20 from the carrier substrate 12.

[0098] Referring to FIG. 13, a laser 200 may provide a laser beam 202 that is used to heat the bonding layer 30 formed of amorphous silicon that bonds the flexible glass substrate 12 and the carrier substrate 20. Laser crystallization, which can utilize high-intensity laser pulses, may be used to heat the amorphous silicon to above its melting point. In some instances, only partial melting of the bonding layer 30 may be needed, for example, at the interfaces between the bonding layer 30 and the flexible glass substrate 20 and/or the carrier substrate 20. The molten silicon will then crystallize as it cools, modifying a topography 204 of the bonding layer 30, which can facilitate debonding of the flexible glass substrate 12. In some embodiments, the topography 204 of the bonding layer 30 can result in regions of force and expansion in the bonding layer 30, which can provide separation of the flexible glass substrate 20 from the carrier substrate 12.

[0099] Any suitable laser energy may be utilized for melting and/or ablating the silicon. As one example, for a HeNe laser 633 nm, a fluence lower than 0.8 J cm^"2 may not melt the silicon surface, but for a fluence higher than 2 J cm^"2, laser ablation of silicon can occur. A laser pulse of 20 ns duration and 1.6 J cm^"2 fluence melts a silicon surface sufficiently without ablation. Other suitable lasers include UV lasers due to the high absorption of silicon. For example, for a XeCl laser 308 nm, a fluence of between about 2 and 5 2 J cm^"2 for a 30 ns pulse may be used to ablate the silicon. As another example, for an ArF laser, a fluence of greater than 1 J cm^"2 for a 12 ns pulse may be used to ablate the silicon. The laser beam may be provided to the bonding layer 30 through the carrier substrate 12 (FIG. 14A), through the flexible glass substrate 20 (FIG. 14B) and/or between the carrier substrate 12 and the flexible glass substrate 20 (i.e., from the side).

[00100] Referring to FIG. 15, the laser 200 may provide the laser beam 202 that is used to ablate the amorphous silicon of the bonding layer 30. By utilizing fluences above the silicon ablation threshold, the bonding layer 30 or at least portions thereof can be reduced to a powder residue 205, thereby facilitating removal of the flexible glass substrate 12 from the carrier substrate 20. The rate at which the silicon can be ablated and the flexible glass substrate 12 removed depends, at least in part, on the laser fluence, pulse frequency and scan speed. To have a faster scan rate, the fluence can be increased as well as the pulse frequency. Focusing the laser closer to the silicon and flexible glass substrate 12 interface can facilitate more effective removal of the flexible glass substrate 12.

[00101] Referring to FIG. 16, in some embodiments, the flexible glass substrate 12 may be separated from the carrier substrate 20 as the amorphous silicon of the bonding layer 30 is melted (as opposed to after the polycrystalline silicon structure is formed as shown by FIG. 13). Melting of the amorphous silicon structure, reduces the bonding strength locally using the laser 202 and laser beam 204, which allows for peel separation of the flexible glass substrate 12 at the melt location 206. As the silicon cools, a polycrystalline layer 208 remains.

Releasing the Flexible Glass Substrate

[00102] Any suitable methods may be utilized for releasing the flexible glass substrate 20 from the carrier substrate 12. As one example, stresses for de-lamination may occur due to a shift in the overall tensile-compressive neutral axis during formation of the final device that utilizes the flexible glass substrate 20. For example, bonding the flexible glass substrate 20 and the carrier substrate 12 together may initially place the bond plane close to the stress neutral axis. When the bond is near the neutral axis, mechanical tensile stresses may be minimized. After a device is fully assembled with the flexible glass substrate 20 bonded to the carrier substrate 12, potentially with a cover glass, the stress neutral axis can shift, which can drastically increase the tensile and bend stresses along the bond plane leading to at least some de-lamination. De-lamination may also be initiated and/or completed using any number of devices such as pry plates, lasers, knives, score wheels, etchants and/or the flexible glass substrate may be removed manually.

[00103] Referring now to FIG. 17, an exemplary bonding layer 30 application pattern is illustrated where the flexible glass substrate 20 is to be divided or diced into multiple segments, sometimes referred to as device units. FIG. 17 illustrates a plan view of a stack 100 includes the flexible glass substrate 20 that is bonded to the carrier substrate 12 as described above. The bonding layer (represented by area Ai) may be applied over the entire (or less than the entire) footprint of the flexible glass substrate 20 on glass support surface 14 of the carrier substrate 12. In the illustrated embodiment, the flexible glass substrate 20 is subdivided into device units 102 (also represented by areas A₂) for further processing having perimeters 104. By applying the bonding layer Ai beneath the device units 102, leakage of process fluids into regions defined by the device units 102, which may contaminate subsequent processes, or may prematurely separate the flexible glass substrate 20 (or at least a portion thereof) from the carrier substrate 12 can be minimized or prevented.

[00104] Although shown as having one flexible glass substrate 20 bonded to the carrier substrate 12, a plurality of flexible glass substrates 20 may be bonded to one carrier substrate 12 or to multiple carrier substrates 12. In these cases, the carrier substrate 12 may be separated from the multiple flexible glass substrates 20 simultaneously or in some suitable sequential fashion.

[00105] Any number of the device units 102 may be separated from any number of the other device units 102 by cutting along the perimeters 104. Venting may be provided to reduce any bulging of or other undesired effects on the flexible glass substrate 20. A laser or other cutting device may be used for cutting the individual device units 102 from the flexible glass sheet 20. Additionally, the cutting may be performed such that only the flexible glass substrate 20 is cut or scored and not the carrier substrate 12 to enable re-use of the carrier substrate 12. Etching and/or any other cleaning process may be used to remove any residue left by the bonding layer 30. Etching may also be used to aid in the removal of the flexible glass substrate 20 from the carrier substrate 12.

[00106] Referring to FIG. 18, an embodiment of a method for removing a device unit 140 of the flexible glass substrate 20, e.g., that unit having electrical devices 145 or other desired structure formed thereon, from the carrier substrate 12 is shown. Any number of device units 140 may be made from a flexible glass substrate 20 bonded to a carrier substrate, depending upon the size of the flexible glass substrate 20 and the size of the device units 140. For example, the flexible glass substrate may be of a Gen 2 size or larger, for example, Gen 3, Gen 4, Gen 5, Gen 8 or larger (e.g., sheet sizes from 100 mm x 100 mm to 3 meters x 3 meters or greater). In order to allow a user to determine an arrangement of device units 140— in terms of size, number, and shape, of the device units 140, for example— that one would like to produce from one flexible glass substrate 20 as bonded to a carrier substrate 12, the flexible glass substrate 20 may be supplied as shown in FIG. 14. More specifically, there is provided a substrate stack 10 having a flexible glass substrate 20 and a carrier substrate 12. The flexible glass substrate 20 is bonded to the carrier substrate 12 in a bonded area 142 that surrounds a non-bonded area 144.

[00107] The bonded area 142 is disposed at the perimeter of the flexible glass substrate 20, completely surrounding the non-bonded area 144. This continuous bonded area 142 can be used to seal any gap between the flexible glass substrate 20 and carrier substrate 12 at the perimeter of the flexible glass substrate 20 so that process fluids are not trapped as otherwise trapped process fluids may contaminate a subsequent process through which the substrate stack 10 is conveyed. However, in other embodiments, a discontinuous bonded area may be used.

[00108] A CO₂ laser beam may be used to cut a perimeter 146 of the desired parts 140. The CO₂ laser enables full body cut (100 percent of the thickness) of the flexible glass substrate 20. For the CO₂ laser cutting, a laser beam is focused into a circular beam shape of small diameter on the surface 24 of the flexible glass substrate 20, and moves along the required trajectory and may be followed by a coolant nozzle. The coolant nozzle may be an air nozzle, for example, which delivers a compressed air stream onto the surface of the thin sheet through a small diameter orifice. Use of water or of air- liquid mist may also be used. Once the perimeter 146 of the device unit 140 is cut, the device unit 140 may be removed from the remaining flexible glass substrate 20. An energy input may then be applied to the bonding layer 30 that changes a structure of the bonding layer 30. The structure change decreases the bond strength of the bonding layer 30 to facilitate separation of the remaining flexible glass substrate 20 from the carrier substrate 12.

[00109] Referring to FIG. 19, an embodiment of a method of releasing the flexible glass substrate 20 from the carrier substrate 12 is illustrated. Once the flexible glass substrate 20 is processed to include the desired devices 150 (e.g., LCD, OLED or TFT electronics) and, for example, the device units 140 are removed, the remaining flexible glass substrate 20 (or the entire flexible glass substrate 20) is released from the carrier substrate 12. In this embodiment, the bonding layer 30 may be formed as a perimeter bond 152 forming a bonded area 154 and a non-bonded area 156. A laser 158 directs a laser beam 160 (e.g., with between about 400 nm and 750 nm wavelength) between the flexible glass substrate 162 and the carrier substrate 12 to locally heat portions of the bonding layer 30. LED and flashlamp sources are also possible that are tuned to the bonding layer 30 absorption. For example, the laser 158 may be used to locally heat and oxidize a carbon-based bonding layer 30. The perimeter bond 152 can facilitate the localized heating of the carbon-based bonding layer 30 by the laser 158, providing greater access to the carbon-based bonding layer 30 due to its proximity to the perimeter of the flexible glass substrate 20 and relatively small cross- sectional area (e.g., compared to a bond across the entire width of the flexible glass substrate 12).

[00110] The above-described bonding layers can provide an inorganic adhesion approach that enables use of thin flexible glass substrates within existing equipment and fabrication conditions. The carrier substrates can be reused with different flexible glass substrates. The stacks including the carrier substrates, flexible glass substrates and bonding layers may be assembled and then shipped for further processing. Alternatively, some or none of the stacks may be assembled prior to shipping. The carrier substrates need not be pristine for use as a carrier substrate. For example, the carrier substrates may have been subjected to excessive cord or streak rendering them unsuitable for use as a display device. The use of the carrier substrate can avoid issues of using thin substrate directly, such as dimpling around vacuum holes and increased electrostatic issues. Height of the bonding layer may be thin (e.g., about 10 μιη or less or between about 1 to 100 μιη), which can minimize flatness issues, such as sag and facilitates use as a continuously applied film across the entire carrier substrate or applied locally, such as around the perimeter.

[00111] In the previous detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of various principles of the present invention. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of various principles of the present invention. Finally, wherever applicable, like reference numerals refer to like elements.

[00112] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[00113] Directional terms as used herein— for example up, down, right, left, front, back, top, bottom— are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[00114] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described herein.

[00115] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a "component" includes aspects having two or more such components, unless the context clearly indicates otherwise.

It should be emphasized that the above-described embodiments of the present invention, particularly any "preferred" embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of various principles of the invention. Many variations and modifications may be made to the above-described embodiments of the invention without departing substantially from the spirit and various principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the following claims.

Claims

What is claimed is:

1. A method of processing a flexible glass substrate, the method comprising:

2. A method of processing a flexible glass substrate, the method comprising:

providing a carrier substrate having a glass support surface;

providing a flexible glass substrate having first and second broad surfaces;

3. The method of claim 2 further comprising providing an energy input to the inorganic bonding layer for changing the structure of the inorganic bonding layer and reducing the bond strength between the flexible glass substrate and the carrier substrate.

4. The method of claim 1 or claim 3, wherein the energy input is thermal energy, or optical energy, that results in heating the inorganic bonding layer to a temperature of at least 250 °C.

5. The method of any one of claims 1-3, wherein the inorganic bonding layer is heated locally using a laser, or a flash lamp.

6. The method of any one of claims 1-3, wherein the inorganic bonding layer comprises an inorganic bonding material located along a perimeter of the flexible glass substrate.

7. The method of any one of claims 1-3, wherein the structural change includes crystallization, increasing a porosity of the inorganic bonding layer, or increasing a microfracture of the inorganic bonding layer.

8. The method of any one of claims 1 or 3 further comprising removing the flexible glass substrate from the carrier substrate after providing the energy input to the inorganic bonding layer.

9. The method of any one of claims 1-3, wherein the bonding material comprises one or more of a glass, a glass ceramic, a ceramic, carbon, and silicon.

10. The method of any one of claims 1 or 3, wherein the input energy is thermal energy, or optical energy, and the method comprising heating the bonding material up to a temperature of at least 250 °C without a reduction of the bond strength.

11. A substrate stack comprising:

a carrier substrate having a glass support surface;

an inorganic bonding layer that bonds the flexible glass substrate to the carrier substrate, the inorganic bonding layer comprising a bond material that changes structure and reduces a bond strength between the flexible glass substrate and the carrier substrate for removing the flexible glass substrate from the carrier substrate.

12. The substrate stack of claim 11, wherein the bond material comprises at least one of a glass, a glass ceramic and a ceramic.

13. The substrate stack of claim 11 or claim 12, wherein the structural change includes crystallization, increasing a porosity of the inorganic bonding layer, or increasing a microfracture of the inorganic bonding layer.